1. Field of Invention
The present invention relates to a multi-functional composite substrate structure, and more particularly, to a multi-functional composite substrate structure adapted for fabricating various built-in passive components.
2. Related Art
With the trend towards high function and high speed of electronic products, various passive components, such as resistors, capacitors, and inductors, have to be integrated on a semiconductor package, so as to enhance or stabilize the electrical functionality of electronic products.
Conventionally, passive components are disposed on the surface of the substrate of a printed circuit board (PCB) or semiconductor chip. However, to satisfy the trend towards high functionality and miniaturization of electronic products, the lamination technique of the circuit board must have advantages such as thinness, multi-layer, and high density. Therefore, to create larger space and improve the multi-functionality of the module in a limited substrate area, the circuit layout and the distance of signal transmission are usually reduced by reducing the area of the passive components or building them inside, thereby creating more space to build active components and improve the performance of the overall components. Therefore, the substrate structure of built-in passive components such as resistors, capacitors, and inductors is provided.
Through building resistors, capacitors, and inductors inside, various components are formed on the circuit substrate during the fabrication of the substrate, so as to enhance the stability of the circuit fabrication, reduce the number of welding spots and the number of passive components on the substrate, and improve the reliability of the fabrication. Moreover, the area of the substrate can be reduced for reducing the fabricating cost of the circuit, thereby conform to the requirements for fabricating substrates in future electronic products. The substrate architecture of conventional built-in components only concentrates on one component or a specific function, thus greatly limiting the application of built-in components for the substrate. However, to optimize the electrical features of various components, it is insufficient to employ only one kind of substrate material. Most conventional arts directed to materials of high dielectric coefficient, so only relative components such as built-in capacitors are designed. In the thick film ceramic process, a substrate structure design integrated with various materials is used, in which different materials can be filled in different areas to fit different components. However, when different materials are used for different blocks, the fabricating cost is increased, the design is complicated, and the process is inaccurate.
Please refer to FIG. 1, a conductive metal sheet 110, a dielectric thin plate 120, and a conductive metal sheet 112 are stacked sequentially to form a capacitive substrate structure 100, as shown in U.S. Pat. No. 5,155,655. The lamination structure can only provide the substrate structure with the capacitive circuit function. Moreover, when the dielectric thin plate 120 is made of high dielectric coefficient materials, there is difficulty in wiring. Besides, when the outside plate has no particular design to increase the electrical property of the transmission line, the lamination structure cannot widely and effectively improve the performance of the substrate.
Referring to FIG. 2, it is a substrate structure made of two special materials. The two special substrate materials are sintered to form a substrate structure 200 formed by interlacely stacking substrates 210, 212, 214 of low dielectric loss and low dielectric constant and substrates 220, 222 of high dielectric constant. The substrate structure 200 can be used to fabricate built-in capacitors and circuits of low dielectric loss, as shown in U.S. Pat. No. 4,882,650. Though many functions of the substrate are added and significantly improved, large inductors of high price still cannot be built inside, while only wires are wound.
In U.S. Pat. No. 6,429,763, magnetic substances are used as substrates and provide the inductive circuit function by winding wires. However, only the inductivity is taken into consideration, while the coupling parasitic effect between other components and the inductor are neglected. Therefore, there is no effective integrated solution directing to the materials of built-in components and the transmission line. Moreover, as the whole substrate uses a magnetic substance, the magnetic field generated cannot be effectively shielded.
As such, most of the substrate structures at present are provided to build specific components inside. Therefore, in order to improve the design and application of various built-in components, it is a trend for those skilled in the art to provide a desired multi-functional substrate structure.